1. Field of the Invention
The present invention relates to a radiator for a motorcycle for reducing noise caused by exhausted cooling air.
2. Description of Background Art
Japanese Utility Model Laid-Open Publication No. Hei 1-162033 discloses a cooling device for a radiator for a motorcycle, in which a cooling fan is positioned at an outlet for the radiator cooling air, and a cylindrical shroud surrounds an impeller for the cooling fan. The shroud has its front open end coupled to the rear periphery of the radiator, and houses a cooling fan at a rear portion. Further, an outlet of the shroud is in the shape of a bell mouth. In the present invention, the front, rear, left and right directions denote directions viewed in the plane which confronts flow of cooling air to the radiator, and an upward and downward direction denote the directions viewed from the position where the radiator is installed.
A shroud surrounding a cooling fan for a radiator is effective in reliably maintaining an amount of cooling air while a motorcycle is stationary and idling or while it is operating at low speeds. However, cooling air flowing through the shroud generates noise. Such noise can be reduced to a certain degree when the shroud uses a bell mouth structure. Since the cooling device of the motorcycle is usually exposed, it has been required to reduce the noise caused by exhausted cooling air as demand for quiet driving has been on the rise recently. Therefore, a cooling device for a radiator of a motorcycle has to not only obtain a necessary amount of cooling air but also reduce the noise resulting from exhausted cooling air.
A radiator is usually cooled by airstreams caused by a moving motorcycle. When the radiator has its rear surface covered by the shroud as in the foregoing publication, cooling air passing through the radiator cannot easily flow outwardly. Therefore, it is also required to improve cooling efficiency while the motorcycle is operating.